【目录】
关键字:Java解析xml、解析xml四种方法、DOM、SAX、JDOM、DOM4j、XPath
【引言】
目前在Java中用于解析XML的技术很多,主流的有DOM、SAX、JDOM、DOM4j,下文主要介绍这4种解析XML文档技术的使用、优缺点及性能测试。
一、【基础知识——扫盲】
sax、dom是两种对xml文档进行解析的方法(没有具体实现,只是接口),所以只有它们是无法解析xml文档的;jaxp只是api,它进一步封装了sax、dom两种接口,并且提供了DomcumentBuilderFactory/DomcumentBuilder和SAXParserFactory/SAXParser(默认使用xerces解释器)。二、【DOM、SAX、JDOM、DOM4j简单使用介绍】
1、【DOM(Document Object Model) 】由W3C提供的接口,它将整个XML文档读入内存,构建一个DOM树来对各个节点(Node)进行操作。
示例代码:
-
<?xml version=“1.0” encoding=“UTF-8”?>
-
<university name=“pku”>
-
<college name=“c1”>
-
<class name=“class1”>
-
<student name=“stu1” sex=‘male’ age=“21” />
-
<student name=“stu2” sex=‘female’ age=“20” />
-
<student name=“stu3” sex=‘female’ age=“20” />
-
</class>
-
<class name=“class2”>
-
<student name=“stu4” sex=‘male’ age=“19” />
-
<student name=“stu5” sex=‘female’ age=“20” />
-
<student name=“stu6” sex=‘female’ age=“21” />
-
</class>
-
</college>
-
<college name=“c2”>
-
<class name=“class3”>
-
<student name=“stu7” sex=‘male’ age=“20” />
-
</class>
-
</college>
-
<college name=“c3”>
-
</college>
-
</university>
后文代码中有使用到text.xml(该文档放在src路径下,既编译后在classes路径下),都是指该xml文档。
-
package test.xml;
-
-
import java.io.File;
-
import java.io.FileNotFoundException;
-
import java.io.FileOutputStream;
-
import java.io.IOException;
-
import java.io.InputStream;
-
-
import javax.xml.parsers.DocumentBuilder;
-
import javax.xml.parsers.DocumentBuilderFactory;
-
import javax.xml.parsers.ParserConfigurationException;
-
import javax.xml.transform.Transformer;
-
import javax.xml.transform.TransformerConfigurationException;
-
import javax.xml.transform.TransformerException;
-
import javax.xml.transform.TransformerFactory;
-
import javax.xml.transform.dom.DOMSource;
-
import javax.xml.transform.stream.StreamResult;
-
-
import org.w3c.dom.Document;
-
import org.w3c.dom.Element;
-
import org.w3c.dom.Node;
-
import org.w3c.dom.NodeList;
-
import org.w3c.dom.Text;
-
import org.xml.sax.SAXException;
-
-
/**
-
* dom读写xml
-
* @author whwang
-
*/
-
public
class TestDom {
-
-
public static void main(String[] args) {
-
read();
-
//write();
-
}
-
-
public static void read() {
-
DocumentBuilderFactory dbf = DocumentBuilderFactory.newInstance();
-
try {
-
DocumentBuilder builder = dbf.newDocumentBuilder();
-
InputStream in = TestDom.class.getClassLoader().getResourceAsStream(
"test.xml");
-
Document doc = builder.parse(in);
-
// root <university>
-
Element root = doc.getDocumentElement();
-
if (root ==
null)
return;
-
System.err.println(root.getAttribute(
"name"));
-
// all college node
-
NodeList collegeNodes = root.getChildNodes();
-
if (collegeNodes ==
null)
return;
-
for(
int i =
0; i < collegeNodes.getLength(); i++) {
-
Node college = collegeNodes.item(i);
-
if (college !=
null && college.getNodeType() == Node.ELEMENT_NODE) {
-
System.err.println(
"\t" + college.getAttributes().getNamedItem(
"name").getNodeValue());
-
// all class node
-
NodeList classNodes = college.getChildNodes();
-
if (classNodes ==
null)
continue;
-
for (
int j =
0; j < classNodes.getLength(); j++) {
-
Node clazz = classNodes.item(j);
-
if (clazz !=
null && clazz.getNodeType() == Node.ELEMENT_NODE) {
-
System.err.println(
"\t\t" + clazz.getAttributes().getNamedItem(
"name").getNodeValue());
-
// all student node
-
NodeList studentNodes = clazz.getChildNodes();
-
if (studentNodes ==
null)
continue;
-
for (
int k =
0; k < studentNodes.getLength(); k++) {
-
Node student = studentNodes.item(k);
-
if (student !=
null && student.getNodeType() == Node.ELEMENT_NODE) {
-
System.err.print(
"\t\t\t" + student.getAttributes().getNamedItem(
"name").getNodeValue());
-
System.err.print(
" " + student.getAttributes().getNamedItem(
"sex").getNodeValue());
-
System.err.println(
" " + student.getAttributes().getNamedItem(
"age").getNodeValue());
-
}
-
}
-
}
-
}
-
}
-
}
-
}
catch (ParserConfigurationException e) {
-
e.printStackTrace();
-
}
catch (FileNotFoundException e) {
-
e.printStackTrace();
-
}
catch (SAXException e) {
-
e.printStackTrace();
-
}
catch (IOException e) {
-
e.printStackTrace();
-
}
-
-
}
-
-
public static void write() {
-
DocumentBuilderFactory dbf = DocumentBuilderFactory.newInstance();
-
try {
-
DocumentBuilder builder = dbf.newDocumentBuilder();
-
InputStream in = TestDom.class.getClassLoader().getResourceAsStream(
"test.xml");
-
Document doc = builder.parse(in);
-
// root <university>
-
Element root = doc.getDocumentElement();
-
if (root ==
null)
return;
-
// 修改属性
-
root.setAttribute(
"name",
"tsu");
-
NodeList collegeNodes = root.getChildNodes();
-
if (collegeNodes !=
null) {
-
for (
int i =
0; i <collegeNodes.getLength() -
1; i++) {
-
// 删除节点
-
Node college = collegeNodes.item(i);
-
if (college.getNodeType() == Node.ELEMENT_NODE) {
-
String collegeName = college.getAttributes().getNamedItem(
"name").getNodeValue();
-
if (
"c1".equals(collegeName) ||
"c2".equals(collegeName)) {
-
root.removeChild(college);
-
}
else
if (
"c3".equals(collegeName)) {
-
Element newChild = doc.createElement(
"class");
-
newChild.setAttribute(
"name",
"c4");
-
college.appendChild(newChild);
-
}
-
}
-
}
-
}
-
// 新增节点
-
Element addCollege = doc.createElement(
"college");
-
addCollege.setAttribute(
"name",
"c5");
-
root.appendChild(addCollege);
-
Text text = doc.createTextNode(
"text");
-
addCollege.appendChild(text);
-
-
// 将修改后的文档保存到文件
-
TransformerFactory transFactory = TransformerFactory.newInstance();
-
Transformer transFormer = transFactory.newTransformer();
-
DOMSource domSource =
new DOMSource(doc);
-
File file =
new File(
"src/dom-modify.xml");
-
if (file.exists()) {
-
file.delete();
-
}
-
file.createNewFile();
-
FileOutputStream out =
new FileOutputStream(file);
-
StreamResult xmlResult =
new StreamResult(out);
-
transFormer.transform(domSource, xmlResult);
-
System.out.println(file.getAbsolutePath());
-
}
catch (ParserConfigurationException e) {
-
e.printStackTrace();
-
}
catch (SAXException e) {
-
e.printStackTrace();
-
}
catch (IOException e) {
-
e.printStackTrace();
-
}
catch (TransformerConfigurationException e) {
-
e.printStackTrace();
-
}
catch (TransformerException e) {
-
e.printStackTrace();
-
}
-
}
-
}
该代码只要稍做修改,即可变得更加简洁,无需一直写if来判断是否有子节点。
2、【SAX (Simple API for XML) 】
SAX不用将整个文档加载到内存,基于事件驱动的API(Observer模式),用户只需要注册自己感兴趣的事件即可。SAX提供EntityResolver, DTDHandler, ContentHandler, ErrorHandler接口,分别用于监听解析实体事件、DTD处理事件、正文处理事件和处理出错事件,与AWT类似,SAX还提供了一个对这4个接口默认的类DefaultHandler(这里的默认实现,其实就是一个空方法),一般只要继承DefaultHandler,重写自己感兴趣的事件即可。
示例代码:
-
package test.xml;
-
-
import java.io.IOException;
-
import java.io.InputStream;
-
-
import javax.xml.parsers.ParserConfigurationException;
-
import javax.xml.parsers.SAXParser;
-
import javax.xml.parsers.SAXParserFactory;
-
-
import org.xml.sax.Attributes;
-
import org.xml.sax.InputSource;
-
import org.xml.sax.Locator;
-
import org.xml.sax.SAXException;
-
import org.xml.sax.SAXParseException;
-
import org.xml.sax.helpers.DefaultHandler;
-
-
/**
-
*
-
* @author whwang
-
*/
-
public
class TestSAX {
-
-
public static void main(String[] args) {
-
read();
-
write();
-
}
-
-
public static void read() {
-
try {
-
SAXParserFactory factory = SAXParserFactory.newInstance();
-
SAXParser parser = factory.newSAXParser();
-
InputStream in = TestSAX.class.getClassLoader().getResourceAsStream(
"test.xml");
-
parser.parse(in,
new MyHandler());
-
}
catch (ParserConfigurationException e) {
-
e.printStackTrace();
-
}
catch (SAXException e) {
-
e.printStackTrace();
-
}
catch (IOException e) {
-
e.printStackTrace();
-
}
-
}
-
-
public static void write() {
-
System.err.println(
"纯SAX对于写操作无能为力");
-
}
-
-
}
-
-
// 重写对自己感兴趣的事件处理方法
-
class MyHandler extends DefaultHandler {
-
-
@Override
-
public InputSource resolveEntity(String publicId, String systemId)
-
throws IOException, SAXException {
-
return
super.resolveEntity(publicId, systemId);
-
}
-
-
@Override
-
public void notationDecl(String name, String publicId, String systemId)
-
throws SAXException {
-
super.notationDecl(name, publicId, systemId);
-
}
-
-
@Override
-
public void unparsedEntityDecl(String name, String publicId,
-
String systemId, String notationName)
throws SAXException {
-
super.unparsedEntityDecl(name, publicId, systemId, notationName);
-
}
-
-
@Override
-
public void setDocumentLocator(Locator locator) {
-
super.setDocumentLocator(locator);
-
}
-
-
@Override
-
public void startDocument() throws SAXException {
-
System.err.println(
"开始解析文档");
-
}
-
-
@Override
-
public void endDocument() throws SAXException {
-
System.err.println(
"解析结束");
-
}
-
-
@Override
-
public void startPrefixMapping(String prefix, String uri)
-
throws SAXException {
-
super.startPrefixMapping(prefix, uri);
-
}
-
-
@Override
-
public void endPrefixMapping(String prefix) throws SAXException {
-
super.endPrefixMapping(prefix);
-
}
-
-
@Override
-
public void startElement(String uri, String localName, String qName,
-
Attributes attributes)
throws SAXException {
-
System.err.print(
"Element: " + qName +
", attr: ");
-
print(attributes);
-
}
-
-
@Override
-
public void endElement(String uri, String localName, String qName)
-
throws SAXException {
-
super.endElement(uri, localName, qName);
-
}
-
-
@Override
-
public void characters(char[] ch, int start, int length)
-
throws SAXException {
-
super.characters(ch, start, length);
-
}
-
-
@Override
-
public void ignorableWhitespace(char[] ch, int start, int length)
-
throws SAXException {
-
super.ignorableWhitespace(ch, start, length);
-
}
-
-
@Override
-
public void processingInstruction(String target, String data)
-
throws SAXException {
-
super.processingInstruction(target, data);
-
}
-
-
@Override
-
public void skippedEntity(String name) throws SAXException {
-
super.skippedEntity(name);
-
}
-
-
@Override
-
public void warning(SAXParseException e) throws SAXException {
-
super.warning(e);
-
}
-
-
@Override
-
public void error(SAXParseException e) throws SAXException {
-
super.error(e);
-
}
-
-
@Override
-
public void fatalError(SAXParseException e) throws SAXException {
-
super.fatalError(e);
-
}
-
-
private void print(Attributes attrs) {
-
if (attrs ==
null)
return;
-
System.err.print(
"[");
-
for (
int i =
0; i < attrs.getLength(); i++) {
-
System.err.print(attrs.getQName(i) +
" = " + attrs.getValue(i));
-
if (i != attrs.getLength() -
1) {
-
System.err.print(
", ");
-
}
-
}
-
System.err.println(
"]");
-
}
-
}
3、【JDOM】
JDOM与DOM非常类似,它是处理XML的纯JAVA API,API大量使用了Collections类,且JDOM仅使用具体类而不使用接口。 JDOM 它自身不包含解析器。它通常使用 SAX2 解析器来解析和验证输入 XML 文档(尽管它还可以将以前构造的 DOM 表示作为输入)。它包含一些转换器以将 JDOM 表示输出成 SAX2 事件流、DOM 模型或 XML 文本文档
示例代码:
-
package test.xml;
-
-
import java.io.File;
-
import java.io.FileOutputStream;
-
import java.io.IOException;
-
import java.io.InputStream;
-
import java.util.List;
-
-
import org.jdom.Attribute;
-
import org.jdom.Document;
-
import org.jdom.Element;
-
import org.jdom.JDOMException;
-
import org.jdom.input.SAXBuilder;
-
import org.jdom.output.XMLOutputter;
-
-
/**
-
* JDom读写xml
-
* @author whwang
-
*/
-
public
class TestJDom {
-
public static void main(String[] args) {
-
//read();
-
write();
-
}
-
-
public static void read() {
-
try {
-
boolean validate =
false;
-
SAXBuilder builder =
new SAXBuilder(validate);
-
InputStream in = TestJDom.class.getClassLoader().getResourceAsStream(
"test.xml");
-
Document doc = builder.build(in);
-
// 获取根节点 <university>
-
Element root = doc.getRootElement();
-
readNode(root,
"");
-
}
catch (JDOMException e) {
-
e.printStackTrace();
-
}
catch (IOException e) {
-
e.printStackTrace();
-
}
-
}
-
-
@SuppressWarnings(
"unchecked")
-
public static void readNode(Element root, String prefix) {
-
if (root ==
null)
return;
-
// 获取属性
-
List<Attribute> attrs = root.getAttributes();
-
if (attrs !=
null && attrs.size() >
0) {
-
System.err.print(prefix);
-
for (Attribute attr : attrs) {
-
System.err.print(attr.getValue() +
" ");
-
}
-
System.err.println();
-
}
-
// 获取他的子节点
-
List<Element> childNodes = root.getChildren();
-
prefix +=
"\t";
-
for (Element e : childNodes) {
-
readNode(e, prefix);
-
}
-
}
-
-
public static void write() {
-
boolean validate =
false;
-
try {
-
SAXBuilder builder =
new SAXBuilder(validate);
-
InputStream in = TestJDom.class.getClassLoader().getResourceAsStream(
"test.xml");
-
Document doc = builder.build(in);
-
// 获取根节点 <university>
-
Element root = doc.getRootElement();
-
// 修改属性
-
root.setAttribute(
"name",
"tsu");
-
// 删除
-
boolean isRemoved = root.removeChildren(
"college");
-
System.err.println(isRemoved);
-
// 新增
-
Element newCollege =
new Element(
"college");
-
newCollege.setAttribute(
"name",
"new_college");
-
Element newClass =
new Element(
"class");
-
newClass.setAttribute(
"name",
"ccccc");
-
newCollege.addContent(newClass);
-
root.addContent(newCollege);
-
XMLOutputter out =
new XMLOutputter();
-
File file =
new File(
"src/jdom-modify.xml");
-
if (file.exists()) {
-
file.delete();
-
}
-
file.createNewFile();
-
FileOutputStream fos =
new FileOutputStream(file);
-
out.output(doc, fos);
-
}
catch (JDOMException e) {
-
e.printStackTrace();
-
}
catch (IOException e) {
-
e.printStackTrace();
-
}
-
}
-
-
}
4、【DOM4j】
dom4j是目前在xml解析方面是最优秀的(Hibernate、Sun的JAXM也都使用dom4j来解析XML),它合并了许多超出基本 XML 文档表示的功能,包括集成的 XPath 支持、XML Schema 支持以及用于大文档或流化文档的基于事件的处理
示例代码:
-
package test.xml;
-
-
import java.io.File;
-
import java.io.FileWriter;
-
import java.io.IOException;
-
import java.io.InputStream;
-
import java.util.List;
-
-
import org.dom4j.Attribute;
-
import org.dom4j.Document;
-
import org.dom4j.DocumentException;
-
import org.dom4j.DocumentHelper;
-
import org.dom4j.Element;
-
import org.dom4j.ProcessingInstruction;
-
import org.dom4j.VisitorSupport;
-
import org.dom4j.io.SAXReader;
-
import org.dom4j.io.XMLWriter;
-
-
/**
-
* Dom4j读写xml
-
* @author whwang
-
*/
-
public
class TestDom4j {
-
public static void main(String[] args) {
-
read1();
-
//read2();
-
//write();
-
}
-
-
public static void read1() {
-
try {
-
SAXReader reader =
new SAXReader();
-
InputStream in = TestDom4j.class.getClassLoader().getResourceAsStream(
"test.xml");
-
Document doc = reader.read(in);
-
Element root = doc.getRootElement();
-
readNode(root,
"");
-
}
catch (DocumentException e) {
-
e.printStackTrace();
-
}
-
}
-
-
@SuppressWarnings(
"unchecked")
-
public static void readNode(Element root, String prefix) {
-
if (root ==
null)
return;
-
// 获取属性
-
List<Attribute> attrs = root.attributes();
-
if (attrs !=
null && attrs.size() >
0) {
-
System.err.print(prefix);
-
for (Attribute attr : attrs) {
-
System.err.print(attr.getValue() +
" ");
-
}
-
System.err.println();
-
}
-
// 获取他的子节点
-
List<Element> childNodes = root.elements();
-
prefix +=
"\t";
-
for (Element e : childNodes) {
-
readNode(e, prefix);
-
}
-
}
-
-
public static void read2() {
-
try {
-
SAXReader reader =
new SAXReader();
-
InputStream in = TestDom4j.class.getClassLoader().getResourceAsStream(
"test.xml");
-
Document doc = reader.read(in);
-
doc.accept(
new MyVistor());
-
}
catch (DocumentException e) {
-
e.printStackTrace();
-
}
-
}
-
-
public static void write() {
-
try {
-
// 创建一个xml文档
-
Document doc = DocumentHelper.createDocument();
-
Element university = doc.addElement(
"university");
-
university.addAttribute(
"name",
"tsu");
-
// 注释
-
university.addComment(
"这个是根节点");
-
Element college = university.addElement(
"college");
-
college.addAttribute(
"name",
"cccccc");
-
college.setText(
"text");
-
-
File file =
new File(
"src/dom4j-modify.xml");
-
if (file.exists()) {
-
file.delete();
-
}
-
file.createNewFile();
-
XMLWriter out =
new XMLWriter(
new FileWriter(file));
-
out.write(doc);
-
out.flush();
-
out.close();
-
}
catch (IOException e) {
-
e.printStackTrace();
-
}
-
}
-
}
-
-
class MyVistor extends VisitorSupport {
-
public void visit(Attribute node) {
-
System.out.println(
"Attibute: " + node.getName() +
"="
-
+ node.getValue());
-
}
-
-
public void visit(Element node) {
-
if (node.isTextOnly()) {
-
System.out.println(
"Element: " + node.getName() +
"="
-
+ node.getText());
-
}
else {
-
System.out.println(node.getName());
-
}
-
}
-
-
@Override
-
public void visit(ProcessingInstruction node) {
-
System.out.println(
"PI:" + node.getTarget() +
" " + node.getText());
-
}
-
}
三、【性能测试】
环境:AMD4400+ 2.0+GHz主频 JDK6.0运行参数:-Xms400m -Xmx400m
xml文件大小:10.7M
结果:
DOM: >581297ms
SAX: 8829ms
JDOM: 581297ms
DOM4j: 5309ms
时间包括IO的,只是进行了简单的测试, 仅供参考!!!!
四、【对比】
1、【DOM】DOM是基于树的结构,通常需要加载整文档和构造DOM树,然后才能开始工作。
优点:
a、由于整棵树在内存中,因此可以对xml文档随机访问
b、可以对xml文档进行修改操作
c、较sax,dom使用也更简单。
缺点:
a、整个文档必须一次性解析完
a、由于整个文档都需要载入内存,对于大文档成本高
2、【SAX】
SAX类似流媒体,它基于事件驱动的,因此无需将整个文档载入内存,使用者只需要监听自己感兴趣的事件即可。
优点:
a、无需将整个xml文档载入内存,因此消耗内存少
b、可以注册多个ContentHandler
缺点:
a、不能随机的访问xml中的节点
b、不能修改文档
3、【JDOM】
JDOM是纯Java的处理XML的API,其API中大量使用Collections类,
优点:
a、DOM方式的优点
b、具有SAX的Java规则
缺点
a、DOM方式的缺点
4、【DOM4J】
这4中xml解析方式中,最优秀的一个,集易用和性能于一身。
五、【小插曲XPath】
XPath 是一门在 XML 文档中查找信息的语言, 可用来在 XML 文档中对元素和属性进行遍历。XPath 是 W3C XSLT 标准的主要元素,并且 XQuery 和 XPointer 同时被构建于 XPath 表达之上。因此,对 XPath 的理解是很多高级 XML 应用的基础。XPath非常类似对数据库操作的SQL语言,或者说JQuery,它可以方便开发者抓起文档中需要的东西。(dom4j也支持xpath)
示例代码:
-
package test.xml;
-
-
import java.io.IOException;
-
import java.io.InputStream;
-
-
import javax.xml.parsers.DocumentBuilder;
-
import javax.xml.parsers.DocumentBuilderFactory;
-
import javax.xml.parsers.ParserConfigurationException;
-
import javax.xml.xpath.XPath;
-
import javax.xml.xpath.XPathConstants;
-
import javax.xml.xpath.XPathExpression;
-
import javax.xml.xpath.XPathExpressionException;
-
import javax.xml.xpath.XPathFactory;
-
-
import org.w3c.dom.Document;
-
import org.w3c.dom.NodeList;
-
import org.xml.sax.SAXException;
-
-
public
class TestXPath {
-
-
public static void main(String[] args) {
-
read();
-
}
-
-
public static void read() {
-
try {
-
DocumentBuilderFactory dbf = DocumentBuilderFactory.newInstance();
-
DocumentBuilder builder = dbf.newDocumentBuilder();
-
InputStream in = TestXPath.class.getClassLoader().getResourceAsStream(
"test.xml");
-
Document doc = builder.parse(in);
-
XPathFactory factory = XPathFactory.newInstance();
-
XPath xpath = factory.newXPath();
-
// 选取所有class元素的name属性
-
// XPath语法介绍: http://w3school.com.cn/xpath/
-
XPathExpression expr = xpath.compile(
"//class/@name");
-
NodeList nodes = (NodeList) expr.evaluate(doc, XPathConstants.NODESET);
-
for (
int i =
0; i < nodes.getLength(); i++) {
-
System.out.println(
"name = " + nodes.item(i).getNodeValue());
-
}
-
}
catch (XPathExpressionException e) {
-
e.printStackTrace();
-
}
catch (ParserConfigurationException e) {
-
e.printStackTrace();
-
}
catch (SAXException e) {
-
e.printStackTrace();
-
}
catch (IOException e) {
-
e.printStackTrace();
-
}
-
}
-
-
}
注意4种解析方法对TextNode(文本节点)的处理:
1、在使用DOM时,调用node.getChildNodes()获取该节点的子节点,文本节点也会被当作一个Node来返回,如:
-
<?xml version="1.0" encoding="UTF-8"?>
-
<university name="pku">
-
<college name="c1">
-
<class name="class1">
-
<student name="stu1" sex='male' age="21" />
-
<student name="stu2" sex='female' age="20" />
-
<student name="stu3" sex='female' age="20" />
-
</class>
-
</college>
-
</university>
-
package test.xml;
-
-
import java.io.FileNotFoundException;
-
import java.io.IOException;
-
import java.io.InputStream;
-
import java.util.Arrays;
-
-
import javax.xml.parsers.DocumentBuilder;
-
import javax.xml.parsers.DocumentBuilderFactory;
-
import javax.xml.parsers.ParserConfigurationException;
-
-
import org.w3c.dom.Document;
-
import org.w3c.dom.Element;
-
import org.w3c.dom.Node;
-
import org.w3c.dom.NodeList;
-
import org.xml.sax.SAXException;
-
-
/**
-
* dom读写xml
-
* @author whwang
-
*/
-
public
class TestDom2 {
-
-
public static void main(String[] args) {
-
read();
-
}
-
-
public static void read() {
-
DocumentBuilderFactory dbf = DocumentBuilderFactory.newInstance();
-
try {
-
DocumentBuilder builder = dbf.newDocumentBuilder();
-
InputStream in = TestDom2.class.getClassLoader().getResourceAsStream(
"test.xml");
-
Document doc = builder.parse(in);
-
// root <university>
-
Element root = doc.getDocumentElement();
-
if (root ==
null)
return;
-
// System.err.println(root.getAttribute("name"));
-
// all college node
-
NodeList collegeNodes = root.getChildNodes();
-
if (collegeNodes ==
null)
return;
-
System.err.println(
"university子节点数:" + collegeNodes.getLength());
-
System.err.println(
"子节点如下:");
-
for(
int i =
0; i < collegeNodes.getLength(); i++) {
-
Node college = collegeNodes.item(i);
-
if (college ==
null)
continue;
-
if (college.getNodeType() == Node.ELEMENT_NODE) {
-
System.err.println(
"\t元素节点:" + college.getNodeName());
-
}
else
if (college.getNodeType() == Node.TEXT_NODE) {
-
System.err.println(
"\t文本节点:" + Arrays.toString(college.getTextContent().getBytes()));
-
}
-
}
-
}
catch (ParserConfigurationException e) {
-
e.printStackTrace();
-
}
catch (FileNotFoundException e) {
-
e.printStackTrace();
-
}
catch (SAXException e) {
-
e.printStackTrace();
-
}
catch (IOException e) {
-
e.printStackTrace();
-
}
-
-
}
-
}
输出的结果是:
-
university子节点数:
3
-
子节点如下:
-
文本节点:[
10,
9]
-
元素节点:college
-
文本节点:[
10]
其中\n的ASCII码为10,\t的ASCII码为9。结果让人大吃一惊,university的子节点数不是1,也不是2,而是3,这3个子节点都是谁呢?为了看得更清楚点,把xml文档改为:
-
<?xml version="1.0" encoding="UTF-8"?>
-
<university name="pku">11
-
<college name="c1">
-
<class name="class1">
-
<student name="stu1" sex='male' age="21" />
-
<student name="stu2" sex='female' age="20" />
-
<student name="stu3" sex='female' age="20" />
-
</class>
-
</college>22
-
</university>
还是上面的程序,输出结果为:
-
university子节点数:
3
-
子节点如下:
-
文本节点:[
49,
49,
10,
9]
-
元素节点:college
-
文本节点:[
50,
50,
10]
其中数字1的ASCII码为49,数字2的ASCII码为50。
2、使用SAX来解析同DOM,当你重写它的public void characters(char[] ch, int start, int length)方法时,你就能看到。
3、JDOM,调用node.getChildren()只返回子节点,不包括TextNode节点(不管该节点是否有Text信息)。如果要获取该节点的Text信息,可以调用node.getText()方法,该方法返回节点的Text信息,也包括\n\t等特殊字符。
4、DOM4j同JDOM
参考:
http://www.docin.com/p-78963650.html
http://wenku.baidu.com/view/b091f9360b4c2e3f5727638b.html
http://kree.iteye.com/blog/668280
</div>
【目录】
关键字:Java解析xml、解析xml四种方法、DOM、SAX、JDOM、DOM4j、XPath
【引言】
目前在Java中用于解析XML的技术很多,主流的有DOM、SAX、JDOM、DOM4j,下文主要介绍这4种解析XML文档技术的使用、优缺点及性能测试。
一、【基础知识——扫盲】
sax、dom是两种对xml文档进行解析的方法(没有具体实现,只是接口),所以只有它们是无法解析xml文档的;jaxp只是api,它进一步封装了sax、dom两种接口,并且提供了DomcumentBuilderFactory/DomcumentBuilder和SAXParserFactory/SAXParser(默认使用xerces解释器)。二、【DOM、SAX、JDOM、DOM4j简单使用介绍】
1、【DOM(Document Object Model) 】由W3C提供的接口,它将整个XML文档读入内存,构建一个DOM树来对各个节点(Node)进行操作。
示例代码:
-
<?xml version=“1.0” encoding=“UTF-8”?>
-
<university name=“pku”>
-
<college name=“c1”>
-
<class name=“class1”>
-
<student name=“stu1” sex=‘male’ age=“21” />
-
<student name=“stu2” sex=‘female’ age=“20” />
-
<student name=“stu3” sex=‘female’ age=“20” />
-
</class>
-
<class name=“class2”>
-
<student name=“stu4” sex=‘male’ age=“19” />
-
<student name=“stu5” sex=‘female’ age=“20” />
-
<student name=“stu6” sex=‘female’ age=“21” />
-
</class>
-
</college>
-
<college name=“c2”>
-
<class name=“class3”>
-
<student name=“stu7” sex=‘male’ age=“20” />
-
</class>
-
</college>
-
<college name=“c3”>
-
</college>
-
</university>
后文代码中有使用到text.xml(该文档放在src路径下,既编译后在classes路径下),都是指该xml文档。
-
package test.xml;
-
-
import java.io.File;
-
import java.io.FileNotFoundException;
-
import java.io.FileOutputStream;
-
import java.io.IOException;
-
import java.io.InputStream;
-
-
import javax.xml.parsers.DocumentBuilder;
-
import javax.xml.parsers.DocumentBuilderFactory;
-
import javax.xml.parsers.ParserConfigurationException;
-
import javax.xml.transform.Transformer;
-
import javax.xml.transform.TransformerConfigurationException;
-
import javax.xml.transform.TransformerException;
-
import javax.xml.transform.TransformerFactory;
-
import javax.xml.transform.dom.DOMSource;
-
import javax.xml.transform.stream.StreamResult;
-
-
import org.w3c.dom.Document;
-
import org.w3c.dom.Element;
-
import org.w3c.dom.Node;
-
import org.w3c.dom.NodeList;
-
import org.w3c.dom.Text;
-
import org.xml.sax.SAXException;
-
-
/**
-
* dom读写xml
-
* @author whwang
-
*/
-
public
class TestDom {
-
-
public static void main(String[] args) {
-
read();
-
//write();
-
}
-
-
public static void read() {
-
DocumentBuilderFactory dbf = DocumentBuilderFactory.newInstance();
-
try {
-
DocumentBuilder builder = dbf.newDocumentBuilder();
-
InputStream in = TestDom.class.getClassLoader().getResourceAsStream(
"test.xml");
-
Document doc = builder.parse(in);
-
// root <university>
-
Element root = doc.getDocumentElement();
-
if (root ==
null)
return;
-
System.err.println(root.getAttribute(
"name"));
-
// all college node
-
NodeList collegeNodes = root.getChildNodes();
-
if (collegeNodes ==
null)
return;
-
for(
int i =
0; i < collegeNodes.getLength(); i++) {
-
Node college = collegeNodes.item(i);
-
if (college !=
null && college.getNodeType() == Node.ELEMENT_NODE) {
-
System.err.println(
"\t" + college.getAttributes().getNamedItem(
"name").getNodeValue());
-
// all class node
-
NodeList classNodes = college.getChildNodes();
-
if (classNodes ==
null)
continue;
-
for (
int j =
0; j < classNodes.getLength(); j++) {
-
Node clazz = classNodes.item(j);
-
if (clazz !=
null && clazz.getNodeType() == Node.ELEMENT_NODE) {
-
System.err.println(
"\t\t" + clazz.getAttributes().getNamedItem(
"name").getNodeValue());
-
// all student node
-
NodeList studentNodes = clazz.getChildNodes();
-
if (studentNodes ==
null)
continue;
-
for (
int k =
0; k < studentNodes.getLength(); k++) {
-
Node student = studentNodes.item(k);
-
if (student !=
null && student.getNodeType() == Node.ELEMENT_NODE) {
-
System.err.print(
"\t\t\t" + student.getAttributes().getNamedItem(
"name").getNodeValue());
-
System.err.print(
" " + student.getAttributes().getNamedItem(
"sex").getNodeValue());
-
System.err.println(
" " + student.getAttributes().getNamedItem(
"age").getNodeValue());
-
}
-
}
-
}
-
}
-
}
-
}
-
}
catch (ParserConfigurationException e) {
-
e.printStackTrace();
-
}
catch (FileNotFoundException e) {
-
e.printStackTrace();
-
}
catch (SAXException e) {
-
e.printStackTrace();
-
}
catch (IOException e) {
-
e.printStackTrace();
-
}
-
-
}
-
-
public static void write() {
-
DocumentBuilderFactory dbf = DocumentBuilderFactory.newInstance();
-
try {
-
DocumentBuilder builder = dbf.newDocumentBuilder();
-
InputStream in = TestDom.class.getClassLoader().getResourceAsStream(
"test.xml");
-
Document doc = builder.parse(in);
-
// root <university>
-
Element root = doc.getDocumentElement();
-
if (root ==
null)
return;
-
// 修改属性
-
root.setAttribute(
"name",
"tsu");
-
NodeList collegeNodes = root.getChildNodes();
-
if (collegeNodes !=
null) {
-
for (
int i =
0; i <collegeNodes.getLength() -
1; i++) {
-
// 删除节点
-
Node college = collegeNodes.item(i);
-
if (college.getNodeType() == Node.ELEMENT_NODE) {
-
String collegeName = college.getAttributes().getNamedItem(
"name").getNodeValue();
-
if (
"c1".equals(collegeName) ||
"c2".equals(collegeName)) {
-
root.removeChild(college);
-
}
else
if (
"c3".equals(collegeName)) {
-
Element newChild = doc.createElement(
"class");
-
newChild.setAttribute(
"name",
"c4");
-
college.appendChild(newChild);
-
}
-
}
-
}
-
}
-
// 新增节点
-
Element addCollege = doc.createElement(
"college");
-
addCollege.setAttribute(
"name",
"c5");
-
root.appendChild(addCollege);
-
Text text = doc.createTextNode(
"text");
-
addCollege.appendChild(text);
-
-
// 将修改后的文档保存到文件
-
TransformerFactory transFactory = TransformerFactory.newInstance();
-
Transformer transFormer = transFactory.newTransformer();
-
DOMSource domSource =
new DOMSource(doc);
-
File file =
new File(
"src/dom-modify.xml");
-
if (file.exists()) {
-
file.delete();
-
}
-
file.createNewFile();
-
FileOutputStream out =
new FileOutputStream(file);
-
StreamResult xmlResult =
new StreamResult(out);
-
transFormer.transform(domSource, xmlResult);
-
System.out.println(file.getAbsolutePath());
-
}
catch (ParserConfigurationException e) {
-
e.printStackTrace();
-
}
catch (SAXException e) {
-
e.printStackTrace();
-
}
catch (IOException e) {
-
e.printStackTrace();
-
}
catch (TransformerConfigurationException e) {
-
e.printStackTrace();
-
}
catch (TransformerException e) {
-
e.printStackTrace();
-
}
-
}
-
}
该代码只要稍做修改,即可变得更加简洁,无需一直写if来判断是否有子节点。
2、【SAX (Simple API for XML) 】
SAX不用将整个文档加载到内存,基于事件驱动的API(Observer模式),用户只需要注册自己感兴趣的事件即可。SAX提供EntityResolver, DTDHandler, ContentHandler, ErrorHandler接口,分别用于监听解析实体事件、DTD处理事件、正文处理事件和处理出错事件,与AWT类似,SAX还提供了一个对这4个接口默认的类DefaultHandler(这里的默认实现,其实就是一个空方法),一般只要继承DefaultHandler,重写自己感兴趣的事件即可。
示例代码:
-
package test.xml;
-
-
import java.io.IOException;
-
import java.io.InputStream;
-
-
import javax.xml.parsers.ParserConfigurationException;
-
import javax.xml.parsers.SAXParser;
-
import javax.xml.parsers.SAXParserFactory;
-
-
import org.xml.sax.Attributes;
-
import org.xml.sax.InputSource;
-
import org.xml.sax.Locator;
-
import org.xml.sax.SAXException;
-
import org.xml.sax.SAXParseException;
-
import org.xml.sax.helpers.DefaultHandler;
-
-
/**
-
*
-
* @author whwang
-
*/
-
public
class TestSAX {
-
-
public static void main(String[] args) {
-
read();
-
write();
-
}
-
-
public static void read() {
-
try {
-
SAXParserFactory factory = SAXParserFactory.newInstance();
-
SAXParser parser = factory.newSAXParser();
-
InputStream in = TestSAX.class.getClassLoader().getResourceAsStream(
"test.xml");
-
parser.parse(in,
new MyHandler());
-
}
catch (ParserConfigurationException e) {
-
e.printStackTrace();
-
}
catch (SAXException e) {
-
e.printStackTrace();
-
}
catch (IOException e) {
-
e.printStackTrace();
-
}
-
}
-
-
public static void write() {
-
System.err.println(
"纯SAX对于写操作无能为力");
-
}
-
-
}
-
-
// 重写对自己感兴趣的事件处理方法
-
class MyHandler extends DefaultHandler {
-
-
@Override
-
public InputSource resolveEntity(String publicId, String systemId)
-
throws IOException, SAXException {
-
return
super.resolveEntity(publicId, systemId);
-
}
-
-
@Override
-
public void notationDecl(String name, String publicId, String systemId)
-
throws SAXException {
-
super.notationDecl(name, publicId, systemId);
-
}
-
-
@Override
-
public void unparsedEntityDecl(String name, String publicId,
-
String systemId, String notationName)
throws SAXException {
-
super.unparsedEntityDecl(name, publicId, systemId, notationName);
-
}
-
-
@Override
-
public void setDocumentLocator(Locator locator) {
-
super.setDocumentLocator(locator);
-
}
-
-
@Override
-
public void startDocument() throws SAXException {
-
System.err.println(
"开始解析文档");
-
}
-
-
@Override
-
public void endDocument() throws SAXException {
-
System.err.println(
"解析结束");
-
}
-
-
@Override
-
public void startPrefixMapping(String prefix, String uri)
-
throws SAXException {
-
super.startPrefixMapping(prefix, uri);
-
}
-
-
@Override
-
public void endPrefixMapping(String prefix) throws SAXException {
-
super.endPrefixMapping(prefix);
-
}
-
-
@Override
-
public void startElement(String uri, String localName, String qName,
-
Attributes attributes)
throws SAXException {
-
System.err.print(
"Element: " + qName +
", attr: ");
-
print(attributes);
-
}
-
-
@Override
-
public void endElement(String uri, String localName, String qName)
-
throws SAXException {
-
super.endElement(uri, localName, qName);
-
}
-
-
@Override
-
public void characters(char[] ch, int start, int length)
-
throws SAXException {
-
super.characters(ch, start, length);
-
}
-
-
@Override
-
public void ignorableWhitespace(char[] ch, int start, int length)
-
throws SAXException {
-
super.ignorableWhitespace(ch, start, length);
-
}
-
-
@Override
-
public void processingInstruction(String target, String data)
-
throws SAXException {
-
super.processingInstruction(target, data);
-
}
-
-
@Override
-
public void skippedEntity(String name) throws SAXException {
-
super.skippedEntity(name);
-
}
-
-
@Override
-
public void warning(SAXParseException e) throws SAXException {
-
super.warning(e);
-
}
-
-
@Override
-
public void error(SAXParseException e) throws SAXException {
-
super.error(e);
-
}
-
-
@Override
-
public void fatalError(SAXParseException e) throws SAXException {
-
super.fatalError(e);
-
}
-
-
private void print(Attributes attrs) {
-
if (attrs ==
null)
return;
-
System.err.print(
"[");
-
for (
int i =
0; i < attrs.getLength(); i++) {
-
System.err.print(attrs.getQName(i) +
" = " + attrs.getValue(i));
-
if (i != attrs.getLength() -
1) {
-
System.err.print(
", ");
-
}
-
}
-
System.err.println(
"]");
-
}
-
}
3、【JDOM】
JDOM与DOM非常类似,它是处理XML的纯JAVA API,API大量使用了Collections类,且JDOM仅使用具体类而不使用接口。 JDOM 它自身不包含解析器。它通常使用 SAX2 解析器来解析和验证输入 XML 文档(尽管它还可以将以前构造的 DOM 表示作为输入)。它包含一些转换器以将 JDOM 表示输出成 SAX2 事件流、DOM 模型或 XML 文本文档
示例代码:
-
package test.xml;
-
-
import java.io.File;
-
import java.io.FileOutputStream;
-
import java.io.IOException;
-
import java.io.InputStream;
-
import java.util.List;
-
-
import org.jdom.Attribute;
-
import org.jdom.Document;
-
import org.jdom.Element;
-
import org.jdom.JDOMException;
-
import org.jdom.input.SAXBuilder;
-
import org.jdom.output.XMLOutputter;
-
-
/**
-
* JDom读写xml
-
* @author whwang
-
*/
-
public
class TestJDom {
-
public static void main(String[] args) {
-
//read();
-
write();
-
}
-
-
public static void read() {
-
try {
-
boolean validate =
false;
-
SAXBuilder builder =
new SAXBuilder(validate);
-
InputStream in = TestJDom.class.getClassLoader().getResourceAsStream(
"test.xml");
-
Document doc = builder.build(in);
-
// 获取根节点 <university>
-
Element root = doc.getRootElement();
-
readNode(root,
"");
-
}
catch (JDOMException e) {
-
e.printStackTrace();
-
}
catch (IOException e) {
-
e.printStackTrace();
-
}
-
}
-
-
@SuppressWarnings(
"unchecked")
-
public static void readNode(Element root, String prefix) {
-
if (root ==
null)
return;
-
// 获取属性
-
List<Attribute> attrs = root.getAttributes();
-
if (attrs !=
null && attrs.size() >
0) {
-
System.err.print(prefix);
-
for (Attribute attr : attrs) {
-
System.err.print(attr.getValue() +
" ");
-
}
-
System.err.println();
-
}
-
// 获取他的子节点
-
List<Element> childNodes = root.getChildren();
-
prefix +=
"\t";
-
for (Element e : childNodes) {
-
readNode(e, prefix);
-
}
-
}
-
-
public static void write() {
-
boolean validate =
false;
-
try {
-
SAXBuilder builder =
new SAXBuilder(validate);
-
InputStream in = TestJDom.class.getClassLoader().getResourceAsStream(
"test.xml");
-
Document doc = builder.build(in);
-
// 获取根节点 <university>
-
Element root = doc.getRootElement();
-
// 修改属性
-
root.setAttribute(
"name",
"tsu");
-
// 删除
-
boolean isRemoved = root.removeChildren(
"college");
-
System.err.println(isRemoved);
-
// 新增
-
Element newCollege =
new Element(
"college");
-
newCollege.setAttribute(
"name",
"new_college");
-
Element newClass =
new Element(
"class");
-
newClass.setAttribute(
"name",
"ccccc");
-
newCollege.addContent(newClass);
-
root.addContent(newCollege);
-
XMLOutputter out =
new XMLOutputter();
-
File file =
new File(
"src/jdom-modify.xml");
-
if (file.exists()) {
-
file.delete();
-
}
-
file.createNewFile();
-
FileOutputStream fos =
new FileOutputStream(file);
-
out.output(doc, fos);
-
}
catch (JDOMException e) {
-
e.printStackTrace();
-
}
catch (IOException e) {
-
e.printStackTrace();
-
}
-
}
-
-
}
4、【DOM4j】
dom4j是目前在xml解析方面是最优秀的(Hibernate、Sun的JAXM也都使用dom4j来解析XML),它合并了许多超出基本 XML 文档表示的功能,包括集成的 XPath 支持、XML Schema 支持以及用于大文档或流化文档的基于事件的处理
示例代码:
-
package test.xml;
-
-
import java.io.File;
-
import java.io.FileWriter;
-
import java.io.IOException;
-
import java.io.InputStream;
-
import java.util.List;
-
-
import org.dom4j.Attribute;
-
import org.dom4j.Document;
-
import org.dom4j.DocumentException;
-
import org.dom4j.DocumentHelper;
-
import org.dom4j.Element;
-
import org.dom4j.ProcessingInstruction;
-
import org.dom4j.VisitorSupport;
-
import org.dom4j.io.SAXReader;
-
import org.dom4j.io.XMLWriter;
-
-
/**
-
* Dom4j读写xml
-
* @author whwang
-
*/
-
public
class TestDom4j {
-
public static void main(String[] args) {
-
read1();
-
//read2();
-
//write();
-
}
-
-
public static void read1() {
-
try {
-
SAXReader reader =
new SAXReader();
-
InputStream in = TestDom4j.class.getClassLoader().getResourceAsStream(
"test.xml");
-
Document doc = reader.read(in);
-
Element root = doc.getRootElement();
-
readNode(root,
"");
-
}
catch (DocumentException e) {
-
e.printStackTrace();
-
}
-
}
-
-
@SuppressWarnings(
"unchecked")
-
public static void readNode(Element root, String prefix) {
-
if (root ==
null)
return;
-
// 获取属性
-
List<Attribute> attrs = root.attributes();
-
if (attrs !=
null && attrs.size() >
0) {
-
System.err.print(prefix);
-
for (Attribute attr : attrs) {
-
System.err.print(attr.getValue() +
" ");
-
}
-
System.err.println();
-
}
-
// 获取他的子节点
-
List<Element> childNodes = root.elements();
-
prefix +=
"\t";
-
for (Element e : childNodes) {
-
readNode(e, prefix);
-
}
-
}
-
-
public static void read2() {
-
try {
-
SAXReader reader =
new SAXReader();
-
InputStream in = TestDom4j.class.getClassLoader().getResourceAsStream(
"test.xml");
-
Document doc = reader.read(in);
-
doc.accept(
new MyVistor());
-
}
catch (DocumentException e) {
-
e.printStackTrace();
-
}
-
}
-
-
public static void write() {
-
try {
-
// 创建一个xml文档
-
Document doc = DocumentHelper.createDocument();
-
Element university = doc.addElement(
"university");
-
university.addAttribute(
"name",
"tsu");
-
// 注释
-
university.addComment(
"这个是根节点");
-
Element college = university.addElement(
"college");
-
college.addAttribute(
"name",
"cccccc");
-
college.setText(
"text");
-
-
File file =
new File(
"src/dom4j-modify.xml");
-
if (file.exists()) {
-
file.delete();
-
}
-
file.createNewFile();
-
XMLWriter out =
new XMLWriter(
new FileWriter(file));
-
out.write(doc);
-
out.flush();
-
out.close();
-
}
catch (IOException e) {
-
e.printStackTrace();
-
}
-
}
-
}
-
-
class MyVistor extends VisitorSupport {
-
public void visit(Attribute node) {
-
System.out.println(
"Attibute: " + node.getName() +
"="
-
+ node.getValue());
-
}
-
-
public void visit(Element node) {
-
if (node.isTextOnly()) {
-
System.out.println(
"Element: " + node.getName() +
"="
-
+ node.getText());
-
}
else {
-
System.out.println(node.getName());
-
}
-
}
-
-
@Override
-
public void visit(ProcessingInstruction node) {
-
System.out.println(
"PI:" + node.getTarget() +
" " + node.getText());
-
}
-
}
三、【性能测试】
环境:AMD4400+ 2.0+GHz主频 JDK6.0运行参数:-Xms400m -Xmx400m
xml文件大小:10.7M
结果:
DOM: >581297ms
SAX: 8829ms
JDOM: 581297ms
DOM4j: 5309ms
时间包括IO的,只是进行了简单的测试, 仅供参考!!!!
四、【对比】
1、【DOM】DOM是基于树的结构,通常需要加载整文档和构造DOM树,然后才能开始工作。
优点:
a、由于整棵树在内存中,因此可以对xml文档随机访问
b、可以对xml文档进行修改操作
c、较sax,dom使用也更简单。
缺点:
a、整个文档必须一次性解析完
a、由于整个文档都需要载入内存,对于大文档成本高
2、【SAX】
SAX类似流媒体,它基于事件驱动的,因此无需将整个文档载入内存,使用者只需要监听自己感兴趣的事件即可。
优点:
a、无需将整个xml文档载入内存,因此消耗内存少
b、可以注册多个ContentHandler
缺点:
a、不能随机的访问xml中的节点
b、不能修改文档
3、【JDOM】
JDOM是纯Java的处理XML的API,其API中大量使用Collections类,
优点:
a、DOM方式的优点
b、具有SAX的Java规则
缺点
a、DOM方式的缺点
4、【DOM4J】
这4中xml解析方式中,最优秀的一个,集易用和性能于一身。
五、【小插曲XPath】
XPath 是一门在 XML 文档中查找信息的语言, 可用来在 XML 文档中对元素和属性进行遍历。XPath 是 W3C XSLT 标准的主要元素,并且 XQuery 和 XPointer 同时被构建于 XPath 表达之上。因此,对 XPath 的理解是很多高级 XML 应用的基础。XPath非常类似对数据库操作的SQL语言,或者说JQuery,它可以方便开发者抓起文档中需要的东西。(dom4j也支持xpath)
示例代码:
-
package test.xml;
-
-
import java.io.IOException;
-
import java.io.InputStream;
-
-
import javax.xml.parsers.DocumentBuilder;
-
import javax.xml.parsers.DocumentBuilderFactory;
-
import javax.xml.parsers.ParserConfigurationException;
-
import javax.xml.xpath.XPath;
-
import javax.xml.xpath.XPathConstants;
-
import javax.xml.xpath.XPathExpression;
-
import javax.xml.xpath.XPathExpressionException;
-
import javax.xml.xpath.XPathFactory;
-
-
import org.w3c.dom.Document;
-
import org.w3c.dom.NodeList;
-
import org.xml.sax.SAXException;
-
-
public
class TestXPath {
-
-
public static void main(String[] args) {
-
read();
-
}
-
-
public static void read() {
-
try {
-
DocumentBuilderFactory dbf = DocumentBuilderFactory.newInstance();
-
DocumentBuilder builder = dbf.newDocumentBuilder();
-
InputStream in = TestXPath.class.getClassLoader().getResourceAsStream(
"test.xml");
-
Document doc = builder.parse(in);
-
XPathFactory factory = XPathFactory.newInstance();
-
XPath xpath = factory.newXPath();
-
// 选取所有class元素的name属性
-
// XPath语法介绍: http://w3school.com.cn/xpath/
-
XPathExpression expr = xpath.compile(
"//class/@name");
-
NodeList nodes = (NodeList) expr.evaluate(doc, XPathConstants.NODESET);
-
for (
int i =
0; i < nodes.getLength(); i++) {
-
System.out.println(
"name = " + nodes.item(i).getNodeValue());
-
}
-
}
catch (XPathExpressionException e) {
-
e.printStackTrace();
-
}
catch (ParserConfigurationException e) {
-
e.printStackTrace();
-
}
catch (SAXException e) {
-
e.printStackTrace();
-
}
catch (IOException e) {
-
e.printStackTrace();
-
}
-
}
-
-
}
注意4种解析方法对TextNode(文本节点)的处理:
1、在使用DOM时,调用node.getChildNodes()获取该节点的子节点,文本节点也会被当作一个Node来返回,如:
-
<?xml version="1.0" encoding="UTF-8"?>
-
<university name="pku">
-
<college name="c1">
-
<class name="class1">
-
<student name="stu1" sex='male' age="21" />
-
<student name="stu2" sex='female' age="20" />
-
<student name="stu3" sex='female' age="20" />
-
</class>
-
</college>
-
</university>
-
package test.xml;
-
-
import java.io.FileNotFoundException;
-
import java.io.IOException;
-
import java.io.InputStream;
-
import java.util.Arrays;
-
-
import javax.xml.parsers.DocumentBuilder;
-
import javax.xml.parsers.DocumentBuilderFactory;
-
import javax.xml.parsers.ParserConfigurationException;
-
-
import org.w3c.dom.Document;
-
import org.w3c.dom.Element;
-
import org.w3c.dom.Node;
-
import org.w3c.dom.NodeList;
-
import org.xml.sax.SAXException;
-
-
/**
-
* dom读写xml
-
* @author whwang
-
*/
-
public
class TestDom2 {
-
-
public static void main(String[] args) {
-
read();
-
}
-
-
public static void read() {
-
DocumentBuilderFactory dbf = DocumentBuilderFactory.newInstance();
-
try {
-
DocumentBuilder builder = dbf.newDocumentBuilder();
-
InputStream in = TestDom2.class.getClassLoader().getResourceAsStream(
"test.xml");
-
Document doc = builder.parse(in);
-
// root <university>
-
Element root = doc.getDocumentElement();
-
if (root ==
null)
return;
-
// System.err.println(root.getAttribute("name"));
-
// all college node
-
NodeList collegeNodes = root.getChildNodes();
-
if (collegeNodes ==
null)
return;
-
System.err.println(
"university子节点数:" + collegeNodes.getLength());
-
System.err.println(
"子节点如下:");
-
for(
int i =
0; i < collegeNodes.getLength(); i++) {
-
Node college = collegeNodes.item(i);
-
if (college ==
null)
continue;
-
if (college.getNodeType() == Node.ELEMENT_NODE) {
-
System.err.println(
"\t元素节点:" + college.getNodeName());
-
}
else
if (college.getNodeType() == Node.TEXT_NODE) {
-
System.err.println(
"\t文本节点:" + Arrays.toString(college.getTextContent().getBytes()));
-
}
-
}
-
}
catch (ParserConfigurationException e) {
-
e.printStackTrace();
-
}
catch (FileNotFoundException e) {
-
e.printStackTrace();
-
}
catch (SAXException e) {
-
e.printStackTrace();
-
}
catch (IOException e) {
-
e.printStackTrace();
-
}
-
-
}
-
}
输出的结果是:
-
university子节点数:
3
-
子节点如下:
-
文本节点:[
10,
9]
-
元素节点:college
-
文本节点:[
10]
其中\n的ASCII码为10,\t的ASCII码为9。结果让人大吃一惊,university的子节点数不是1,也不是2,而是3,这3个子节点都是谁呢?为了看得更清楚点,把xml文档改为:
-
<?xml version="1.0" encoding="UTF-8"?>
-
<university name="pku">11
-
<college name="c1">
-
<class name="class1">
-
<student name="stu1" sex='male' age="21" />
-
<student name="stu2" sex='female' age="20" />
-
<student name="stu3" sex='female' age="20" />
-
</class>
-
</college>22
-
</university>
还是上面的程序,输出结果为:
-
university子节点数:
3
-
子节点如下:
-
文本节点:[
49,
49,
10,
9]
-
元素节点:college
-
文本节点:[
50,
50,
10]
其中数字1的ASCII码为49,数字2的ASCII码为50。
2、使用SAX来解析同DOM,当你重写它的public void characters(char[] ch, int start, int length)方法时,你就能看到。
3、JDOM,调用node.getChildren()只返回子节点,不包括TextNode节点(不管该节点是否有Text信息)。如果要获取该节点的Text信息,可以调用node.getText()方法,该方法返回节点的Text信息,也包括\n\t等特殊字符。
4、DOM4j同JDOM
参考:
http://www.docin.com/p-78963650.html
http://wenku.baidu.com/view/b091f9360b4c2e3f5727638b.html
http://kree.iteye.com/blog/668280
</div>